Techniques to provide physical resource allocation using a tree-based structure and communicate a channel quality indicator

ABSTRACT

In a wireless network, simultaneous support of distributed and contiguous sub-carrier allocation may be accomplished in the same sub-frame or time zone. Techniques are described herein that can be used to allocate distributed and/or contiguous basic (physical) resource blocks to users by specifying a codebook index and parent node. Techniques are described herein that can be used to flexibly set a number of sub-channels over which a subscriber station indicates a channel quality indicator to a base station. Sub-channels may be represented as nodes and may be grouped to include a parent node and child nodes. By specifying a code book to use and a parent node, the channel quality indicator of the parent and children nodes can be indicated.

RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 11/562,498, entitled “TECHNIQUES TO PROVIDE A CHANNEL QUALITYINDICATOR” filed on Nov. 22, 2006 and claims priority there from.

FIELD

The subject matter disclosed herein relates to techniques to providephysical resource allocation using a tree-based structure andcommunicate a channel quality indicator.

RELATED ART

Wireless access networks that use a multi-carrier access technique, suchas orthogonal frequency division multiple access (OFDMA), allow thesub-channels and time-slots of a frame to be assigned to several users.Sub-channel quality and achievable throughput for each user may varyover time. Channel quality indicator (CQI) is a measure of sub-channelquality. Sub-channels may be allocated to users based on a variety offactors including but not limited to CQI. For example, CQI can be usedto determine an appropriate modulation and coding scheme (MCS) to beapplied to signals transmitted to a receiver. Communication of CQI usesbandwidth that could otherwise be used to communicate other informationsuch as data. It is desirable to accurately communicate CQI while takinginto account limitations of available bandwidth.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention are illustrated by way of example,and not by way of limitation, in the drawings and in which likereference numerals refer to similar elements.

FIG. 1 shows an example of partitioning of sub-carriers that span asystem bandwidth into sub-channels, in accordance with some embodimentsof the present invention.

FIG. 2 depicts a tree representation of sub-channel blocks, inaccordance with some embodiments of the present invention.

FIGS. 3A and 3B depict examples to allocate physical resource blocks toone or more users, in accordance with some embodiments of the presentinvention.

FIG. 4 depicts an example system that includes a base station andsubscriber station, in accordance with some embodiments of the presentinvention.

FIG. 5 depicts a process that can be used to allocate blocks to one ormore user, in accordance with some embodiments of the present invention.

FIG. 6 depicts an example process that can be used to identify a channelquality indicator of one or more sub-channel, in accordance with someembodiments of the present invention.

DETAILED DESCRIPTION

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the present invention. Thus, theappearances of the phrase “in one embodiment” or “an embodiment” invarious places throughout this specification are not necessarily allreferring to the same embodiment. Furthermore, the particular features,structures, or characteristics may be combined in one or moreembodiments.

In accordance with some embodiments, techniques are provided that arecapable of identifying available basic resource blocks, determiningpossible tree structures for the basic resource blocks, selecting one ormore tree structure from the possible tree structures, storing the oneor more selected tree structure in a codebook, and allocating one ormore basic resource block to a subscriber by indicating a code-bookindex and parent node.

In accordance with some embodiments, techniques are provided that arecapable to selectively determine a channel quality indicator over agroup of one or more sub-channel in response to receipt of a request todetermine channel quality indicator for the group and to transmit thedetermined channel quality indicator. In accordance with someembodiments, bandwidth allocable to transmission of channel qualityindicator is adjustable based in part on a number of sub-channels in thegroup. In accordance with some embodiments, the request to determinechannel quality indicator includes identification of a codebook. Inaccordance with some embodiments, the request to determine channelquality indicator includes identification of a parent node of the group.

Embodiments of the invention may be used in a variety of applications.Some embodiments of the invention may be used in conjunction withvarious devices and systems, for example, a transmitter, a receiver, atransceiver, a transmitter-receiver, a wireless communication station, awireless communication device, a wireless Access Point (AP), a modem, awireless modem, a Personal Computer (PC), a desktop computer, a mobilecomputer, a laptop computer, a notebook computer, a tablet computer, aserver computer, a handheld computer, a handheld device, a PersonalDigital Assistant (PDA) device, a handheld PDA device, a network, awireless network, a Local Area Network (LAN), a Wireless LAN (WLAN), aMetropolitan Area Network (MAN), a Wireless MAN (WMAN), a Wide AreaNetwork (WAN), a Wireless WAN (WWAN), devices and/or networks operatingin accordance with existing IEEE 802.11, 802.11a, 802.11b, 802.11e,802.11g, 802.11h, 802.11i, 802.11n, 802.16, 802.16d, 802.16e, and802.16m standards and/or future versions and/or derivatives and/or LongTerm Evolution (LTE) of the above standards, a Personal Area Network(PAN), a Wireless PAN (WPAN), units and/or devices which are part of theabove WLAN and/or PAN and/or WPAN networks, one way and/or two-way radiocommunication systems, cellular radio-telephone communication systems, acellular telephone, a wireless telephone, a Personal CommunicationSystems (PCS) device, a PDA device which incorporates a wirelesscommunication device, a Multiple Input Multiple Output (MIMO)transceiver or device, a Single Input Multiple Output (SIMO) transceiveror device, a Multiple Input Single Output (MISO) transceiver or device,a Multi Receiver Chain (MRC) transceiver or device, a transceiver ordevice having “smart antenna” technology or multiple antenna technology,or the like. Some embodiments of the invention may be used inconjunction with one or more types of wireless communication signalsand/or systems, for example, Radio Frequency (RF), Infra Red (IR),Frequency-Division Multiplexing (FDM), Orthogonal FDM (OFDM), OrthogonalFrequency Division Multiple Access (OFDMA), Time-Division Multiplexing(TDM), Time-Division Multiple Access (TDMA), Extended TDMA (E-TDMA),General Packet Radio Service (GPRS), Extended GPRS, Code-DivisionMultiple Access (CDMA), Wideband CDMA (WCDMA), CDMA 2000, Multi-CarrierModulation (MDM), Discrete Multi-Tone (DMT), Bluetooth®, ZigBee™, or thelike. Embodiments of the invention may be used in various otherapparatuses, devices, systems and/or networks.

Resource allocation in OFDMA systems such as but not limited to 802.16e,802.16m, or Third Generation Partnership Project (3GPP) LTE may involveassignment of groups of sub-carriers which are referred to assub-channels (802.16e) or chunks (LTE) in frequency and symbols orgroups of symbols which referred to as slots (802.16e) or sub-frames(LTE) in time. A subscriber station receiver may measure channel qualityof transmitted resource blocks and provide channel quality indicator(CQI) to the base station, thereby allowing the base station schedulerto take advantage of channel variations in both time and frequency.

Two approaches to organize sub-carriers into sub-channels include (1)distributed or diversity sub-carrier permutation and (2) contiguoussub-carrier permutation. Both types of sub-channelization schemes aresupported at least in 3GPP LTE and are defined as WorldwideInteroperability for Microwave Access (WiMAX). WiMAX indicatescompliance at least with IEEE 802.16 (2001). Under WiMAX, adaptivecoding and modulation sub-channels may use contiguous allocation whereaspartially used sub-carriers (PUSC) and fully used sub-carriers (FUSC)schemes may use distributed permutation. Other approaches to organizesub-carriers to sub-channels may be used such as but not limited toOptional Partial Usage of Subchannels (OPUSC) and Tile Usage of SubChannels (TUSC).

Under the distributed sub-carrier permutation approach, differentsub-carriers are pseudo-randomly distributed or evenly spaced across thechannel bandwidth. The distributed sub-carrier permutation may maximizefrequency diversity and average out inter-cell interference. This schememay be useful for a mobile environment where channel characteristicschange fast.

Under the contiguous sub-carrier allocation approach, a sub-channel is acontiguous block of sub-carriers which can be adaptively selected by thebase station scheduler. Sub-carriers with the highestsignal-to-interference-plus-noise ratio (SINR) may be chosen, andsub-carriers in deep fades may be avoided. This approach may allowfrequency selective scheduling, and may work well with beam-forming. Apossible limitation of this approach may be that relatively stableconditions are desirable, where the characteristics of the channelchange slowly such as with low-speed or nomadic usage.

Because both allocation schemes have their advantages depending on thesubscriber mix and quality of service (QoS) needs, it may be desirableto support both types of sub-channelization schemes simultaneously toallow operation under different channel conditions.

CQI feedback may be simple when only one sub-channelization scheme issupported in a given subframe (e.g., LTE) or time zone (e.g., WiMAX). Insuch case, CQI feedback for every chunk or sub-channel corresponds tothe sub-channelization scheme signaled for the entire time zone. Inorder to accommodate users of varying mobility and channel profiles inthe same time zone or subframe, CQI feedback information may identifythe sub-channel and time slot that is being allocated and also thesub-channelization scheme. This information may provide the base stationgreater flexibility in guaranteeing QoS for delay sensitive applicationsfor subscribers with both low and high mobility. For example, in orderto report the CQI for a specific sub-channel, the CQI may be sent withthe sub-channel index. As the bandwidth and the number of sub-channelsincreases, the number of bits required to signal the sub-channel indexincreases. Due to bandwidth limitations, it may be necessary to limitthe number of bits provided from a subscriber station to a base stationin connection with communication of a CQI.

In accordance with some embodiments of the present invention, techniquesare provided to permit flexible selection of granularity of CQI feedbackreporting in systems that support at least contiguous or distributedsub-carrier allocation. For simplicity, assume that a resource blockspans the entire OFDMA frame duration in time, although the resourceblock need not span the entire OFDMA frame duration in time. FIG. 1shows an example of partitioning of sub-carriers that span a systembandwidth into 16 sub-channels. FIG. 2 depicts a tree representation ofsub-channel blocks as nodes. The base station may partition the totalavailable sub-carriers into two sets: one set for distributed allocationand one set for contiguous allocation. A base station may define acollection or group of sub-carriers localized in time and frequency(i.e., one-dimensional physical resource blocks) as one or more codebookand allocate one or more codebook physical resource blocks to at leastone subscriber station in the network. In the codebook, a group ofcontiguous or distributed physical resource blocks can be assigned to aspecific user in an uplink to the base station or downlink from the basestation at any time. For example, each node under a parent node may usethe same sub-channelization scheme (e.g., distributed or contiguous).Each parent node has two child nodes in a binary tree structure. Thenodes at the bottom of the tree represent the actual physical resourceblocks that could be either contiguous or non-contiguous. The smallestresource block may define the lowest level in the tree. The smallestresource block may define the physical resource and may be equivalent toa sub-channel. In the tree, the parent node may be an aggregation ofbasic resource blocks under this parent.

In accordance with some embodiments, such a unified sub-channelorganization may have at least one or more of the following properties:(1) simultaneous support of distributed and contiguous sub-carrierallocation in the same OFDM(A) subframe or time zone and (2) flexiblepartitioning between distributed and contiguous sub-channels dependingon the mobility of the subscriber such that the number of sub-channelswith distributed and contiguous sub-channels can be changed dynamicallydepending at least on the mobility of the subscribers.

In some embodiments, a unified CQI feedback signaling scheme can be usedfor both distributed and contiguous sub-carrier allocation of varyinggranularities to control CQI feedback scheduling overhead. In someembodiments, to request a CQI for one or more node, the base station mayidentify a codebook to use and a parent node in the codebook. In someembodiments, the CQI reported at the parent node can be used as anapproximation of the CQI of all the sub-channels at the correspondingterminal branches (e.g., child nodes). The number of child nodes under aparent node can be configured dynamically to adapt at least to thenumber of subscribers, the channel conditions, and feedback constraints.The more nodes a CQI represents, the less bandwidth may be used tocommunicate CQI of the parent and child nodes.

For the example of FIG. 2, when the feedback granularity is 1sub-channel, there are 16 CQI feedback values for each user in everyframe. The channel can be either frequency selective or flat. With flatfading, all sub-carriers that form a sub-channel can be assumed to havethe same fading characteristics. When the channel is flat across morethan one sub-channel, this may allow aggregation of CQI with coarsergranularity. If the channel is approximately flat (i.e., a frequencynon-selective channel) across more than one sub-channel, the CQIoverhead can be reduced by aggregating the CQI corresponding tosub-carriers of two or more sub-channels into one value. For example,when the feedback granularity is 2, 4, 8 and 16 sub-channels, the CQIfeedback overhead may be reduced to respective 8, 4, 2 and 1 CQIfeedback value for each user in every frame. Although not a necessaryfeature of any embodiment, flexibility to reduce the amount of CQIfeedback for multiple sub-channels may permit flexibility to modifybandwidth allocated for CQI feedback.

In the example of FIG. 2, different CQI feedback granularities areapplied to physical resource blocks. For example, a CQI provided forparent node A also represents CQI for 6 child nodes under parent node A.For example, a CQI provided for parent node B also represents CQI for 6child nodes under parent node B. For example, a CQI provided for parentnode C also represents CQI for 14 child nodes under parent node C. Inthis example, the number of CQI values reported per user is reduced from16 values per frame to 3 values per frame. Other levels of granularitymay be applied such that a CQI of a parent node may represent CQI of anynumber of children nodes. Therefore, the CQI reported at the parent nodecan reflect the CQI of all the sub-channel groups (the physical resourceblocks) at the corresponding child nodes.

For example, a CQI for distributed sub-carriers can be represented by anaverage CQI over all sub-carriers that form a resource block. In thecase of contiguous sub-carrier allocation, CQI can be reported on eachindividual sub-channel, or a group of sub-channels with similar channelresponse depending on the available CQI bandwidth and channel frequencyselectivity. The CQI for contiguous sub-carriers can be assumed to bethe average CQI of the set of sub-carriers that form the resource block.For a given amount of spectrum, sub-carrier spacing is fixed and thenumber of sub-carriers per sub-channel may also be fixed. This may helpidentify the sub-channel, constituent sub-carriers, and the centersubcarrier.

In some embodiments, although not a necessary feature of any embodiment,flexible bandwidth allocation of bandwidth used for CQI feedback cansignificantly improve uplink and downlink system capacity and QoS ofOFDMA based systems such as current and next generation of mobile WiMAXand 3GPP LTE.

In some embodiments, although not a necessary feature of any embodiment,improved frequency diversity and interference averaging may result atthe expense of frequency selective scheduling gain. In some embodiments,CQI feedback can be applied to contiguous sub-channels at differentlevels of granularity for optimal trade off between scheduling gain andfeedback overhead.

For example, because distributed sub-channelization uses significantlyless feedback overhead, CQI feedback can begin with distributedsub-channelization over all available sub-carriers. If feedback overheadis within acceptable limits, some sub-channels can be allocated withcontiguous sub-carriers and this number of such sub-channels can beincreased to facilitate subscribers to opportunistically take advantageof frequency selective scheduling gain. Other sub-channel allocationschemes can be used to take advantage of flexible bandwidth allocationto CQI.

FIGS. 3A and 3B depict examples of tree-based resource allocation, inaccordance with some embodiments of the present invention. This examplerefers to an L level tree structure, where L is 3, and each codebook has2^(K) entries, where K is 2. Other sizes of tree structures and numberof entries in a code book can be used. Referring to FIG. 3A, in thisexample, 2^(L−1) (four) basic resource blocks can be allocated to mobileusers. The blocks are labeled 1-4. Basic resource blocks can be spreadover the entire bandwidth to overcome the frequency-selectivity of thecommunication channel and utilize frequency selective scheduling. Giventhat L is 3, the possible tree structures are (2^(L−1))!, which is 24.Eight of the 24 possible tree structures are shown in FIG. 3A.

A small percentage of the (2^(L−1))! possible tree structures may beuseful. Therefore, if 2^(K) of the pre-determined candidate permutationsare selected for use where 2^(K)<<(2^(L−1))!, then a codebook of size2^(K)×(2^(L−1)) can be constructed.

In this example, K is selected to be 2, and accordingly, 2^(K) of thepossible tree structures are selected and stored in a codebook. FIG. 3Bdepicts four selected tree structures. The selection of the treestructures can be random or based on certain criteria used by the basestation scheduler such as consideration of user mobility as well asother factors. An example codebook is shown in FIG. 3B. The codebook canbe arranged such that each row of the codebook includes one of theselected tree structures. Therefore, the ith row (i=0, 1, . . . ,2^(K)−1) of the codebook refers to one of the selected tree structuresshown. Each row of the codebook may correspond to a unique code bookindex.

Allocation of resource blocks can be made by identifying which treestructure to use by identifying a codebook index (i.e., the row numberof the codebook) and by identifying a parent node of the tree structurethat contains basic resource blocks that are assigned to the user. Aparent node index may be used to identify the parent node in the tree.

As an example, to assign blocks 3 and 4 from the tree structure havingcodebook index ‘11’ shown in FIG. 3B to a user, the specified codebookindex is ‘11’ and the specified node index is ‘1’. Therefore, the‘11’+‘1’ specify the basic resource blocks numbered 3 and 4 that areassigned to that mobile station. The mobile station has the samecodebook as the base station and the mobile station understands how tofind and process the allocated basic resource blocks using the codebookindex and node index.

The codebook can be populated by pseudo-randomly selected candidatepermutations from the set of all possible permutations and the codebookindex can further be randomly selected (a frequency hopping pattern).This special case may provide frequency diversity.

FIG. 4 depicts an example system that includes base station 400 andsubscriber station 450, in accordance with some embodiments. Forsimplicity, only one subscriber station is shown, but the system caninclude multiple subscriber stations that are similar to subscriberstation 450. For example, the system may be a wireless access networkthat uses a multi-carrier access technique such as but not limited toOFDM or OFDMA.

In any OFDMA system, the format of sub-carrier organization (e.g.,distributed or contiguous) may be explicitly broadcasted by base station400 to all subscribers. In some embodiments, base station 400 candynamically change the granularity of CQI feedback and thesub-channelization scheme for every sub-channel depending at least onsubscriber mobility and load on the system. Base station may communicatesuch changes to subscriber stations.

In some embodiments, base station 400 may include system configurationlogic 402, QoS requirements and service flow mapping logic 404,requested resources and queue state logic 406, code book data base logic408, CQI management logic 410, and base station (BS) scheduler and frameassembler logic 412.

System configuration logic 402 may indicate one or more sub-channel forwhich CQI is to be measured. QoS requirements and service flow mappinglogic 404 may maintain information related to quality of service andservice flow for subscribers in a network. Requested resources and queuestate logic 406 may manage rates downlink and uplink bandwidth allocatedto subscribers. Codebook database logic 408 may dynamically select acodebook based on balance of many factors including but not limited toresources available and QoS requests. CQI management logic 410 maygenerate a message to be transmitted to a subscriber station to requestCQI feedback from one or more subscriber station for one or moresub-channel based in part on bandwidth allocated for use to provide CQIfeedback.

Base station (BS) scheduler and frame assembler logic 412 may allocatebandwidth based on subscriber needs. BS scheduler and frame assemblerlogic 412 may allocate a region in a subframe for each unique subscriberstation. BS scheduler and frame assembler logic 412 may indicate alocation of a region in a subframe allocated for a subscriber station.BS scheduler and frame assembler logic 412 may set the bandwidthavailable for uplink communication from a subscriber station to a basestation and vice versa. For example, to increase bandwidth of data onuplink, BS scheduler and frame assembler logic 412 may reduce bandwidthallocated to communication of CQI. For example, to reduce bandwidthallocated to communication of CQI, BS scheduler and frame assemblerlogic 412 may reduce the granularity of CQI feedback. BS scheduler andframe assembler logic 412 may provide frames for transmission tosubscriber station 450.

Base station 400 may transmit to subscriber 450 a codebook selectionsignal, CQI granularity signal, and resource allocation signal. Codebookselection signal may indicate a codebook to use. For example, basestation may provide to each subscriber station 2^(K) codebooks, where kis a number of bits in codebook selection signal. The codebook selectionsignal may indicate the codebook among the available codebooks to use.The CQI granularity signal may indicate the parent node for which asubscriber station is to make a CQI measurement. In some embodiments,all nodes under the parent node use the same sub-channelization schemeas the parent node. In some embodiments, the base station may take theCQI of nodes under the parent as having the same CQI as reported forthat of the parent. Resource allocation signal may indicate to thesubscriber station where data is located in a received frame.

Subscriber station 450 may include scheduler and grant management logic452 and CQI measurement logic 454. Subscriber station 450 may store oneor more codebook provided by a base station. Based on an identifiedcodebook in a codebook selection signal, subscriber station 450 mayselect a codebook for use. The codebook may indicate sub-carrierallocation and channelization techniques used for each sub-carrier. Toreduce the complexity of the codebook search, the codebook entries maybe structured in a pre-determined pattern such that depending on thedesired permutation scheme, the appropriate codebook index can bedetermined. The first entry of the codebook however may be thenon-permuted physical resource block index used for localized physicalresource assignments.

Based on the parent node identified in a CQI granularity signal and thesub-channels associated with the parent node and sub-channelizationscheme indicated by the identified codebook, subscriber station 450 maymeasure a CQI at least for the parent node and the related child nodes.When a parent node and related child nodes use a distributedsub-channelization scheme, a common channel quality indicator over thespecified group of a parent node and related child nodes may represent aCQI for a parent node and related child nodes. When a parent node andrelated child nodes use a contiguous sub-channelization scheme, a CQImeasurement of approximately a center sub-channel of the group mayrepresent the common CQI for a parent node and related child nodes, butthe CQI measurement of the group is not limited to this measurement. Anytechniques may be used to measure channel quality indicator, such as butnot limited to Signal to Interference-plus-Noise Ratio (SINR)measurements, Modulation and Coding Scheme (MCS) option selection, andinstantaneous rate feedback.

Subscriber station 450 may indicate the CQI to base station 400 bytransmitting a CQI report signal. The manner by which CQI is reportedmay comply with applicable standards such as but not limited to SINRmeasurements, Modulation and Coding Scheme (MCS) option selection, andinstantaneous rate feedback.

FIG. 5 depicts an example process that can be used to allocate resourceblocks, in accordance with some embodiments of the present invention.Block 502 may include identifying basic resource blocks that can beallocated to one or more mobile subscriber station. For example, thenumber of basic resource blocks may depend on the number of levels in atree structure. For example, 2^(L−1) resource blocks may be available,where L is a number of levels in a tree structure.

Block 504 may include determining possible tree structures for the basicresource blocks. For example, the number of possible tree structures forthe basic resource blocks may be

(2^(L−1))!, where L is a number of levels in a tree structure.

Block 506 may include selecting tree structures and storing the treestructures in a codebook. For example, a code book may be set to have2^(K) entries. For example, a tree with L levels may have (2^(L−1))!possible tree structures. A small percentage of the (2^(L−1))! possibletree structures may be useful. 2^(K) of the pre-determined candidatepermutations may be selected for use, where 2^(K)<<(2^(L−1))!. Theselection can be random or based on certain criteria used by the basestation scheduler such as but not limited to consideration of usermobility.

The code book can be arranged such that each row of the codebookincludes one of the selected tree structures. Each row of the codebookmay correspond to a unique code book index. The code book can becommunicated by a base station to one or more subscriber station.

Block 508 may include allocating one or more resource block for use byone or more subscriber station. To allocate one or more resource block,a tree structure and parent node in the tree may be identified. A treestructure to use may be identified by identifying a codebook index(i.e., the row number of the codebook). A parent node of the treestructure contains basic resource blocks that are assigned to the user.

FIG. 6 depicts an example process that can be used to identify a CQI ofone or more sub-channel, in accordance with some embodiments of thepresent invention. In block 602, a base station may identify a codebookto use. The base station has flexibility to allocate sub-channels to useany sub-channelization scheme such as but not limited to distributed orcontiguous. The codebook may specify a sub-channelization scheme to usefor a sub-channel. Sub-channels may be grouped in a tree arrangement.Sub-channels that use similar sub-channelization schemes may be groupedtogether.

In block 604, base station may request channel quality indicatordetermination for a group of one or more sub-channel. For example, thebase station may request measurement of channel quality indicator of oneor more sub-channel by specifying a parent node. In some embodiments,sub-channels may be accessible in a code-book in a tree arrangement asnodes. A parent node may have two or more child nodes. A subscriberstation may determine whether a channel quality indicator is to bedetermined for one or more nodes by determining whether there are anynodes under the parent node. In some embodiments, the granularity ofchannel quality index may be identified by whether the parent nodeincludes any child nodes. In some embodiments, a channel qualityindicator provided for the parent may represent channel quality of childnodes.

In block 606, a subscriber station may measure CQI of the identifiedgroup. For a parent node and related child nodes (if any) that use adistributed sub-channelization scheme, a common channel qualityindicator over the specified group of sub-channels may be a CQI for theparent node and related child nodes. For a parent node and related childnodes (if any) that use a contiguous sub-channelization scheme, a CQImeasurement of a center sub-channel of the group may be the common CQIfor the parent node and related child nodes, but the CQI measurement ofthe group is not limited to this measurement. CQI measurement techniquesmay include but not limited to SINR, MCS option selection, andinstantaneous rate feedback.

In block 608, the subscriber station may report a CQI of the identifiedgroup to the base station. The format of the CQI report signal may be incompliance with applicable standards such as but not limited to SINR,MCS option selection, and instantaneous rate feedback.

Embodiments of the present invention may be implemented as any or acombination of: one or more microchips or integrated circuitsinterconnected using a parentboard, hardwired logic, software stored bya memory device and executed by a microprocessor, firmware, anapplication specific integrated circuit (ASIC), and/or a fieldprogrammable gate array (FPGA). The term “logic” may include, by way ofexample, software or hardware and/or combinations of software andhardware.

Embodiments of the present invention may be provided, for example, as acomputer program product which may include one or more machine-readablemedia having stored thereon machine-executable instructions that, whenexecuted by one or more machines such as a computer, network ofcomputers, or other electronic devices, may result in the one or moremachines carrying out operations in accordance with embodiments of thepresent invention. A machine-readable medium may include, but is notlimited to, floppy diskettes, optical disks, CD-ROMs (Compact Disc-ReadOnly Memories), and magneto-optical disks, ROMs (Read Only Memories),RAMs (Random Access Memories), EPROMs (Erasable Programmable Read OnlyMemories), EEPROMs (Electrically Erasable Programmable Read OnlyMemories), magnetic or optical cards, flash memory, or other type ofmedia/machine-readable medium suitable for storing machine-executableinstructions.

Moreover, embodiments of the present invention may also be downloaded asa computer program product, wherein the program may be transferred froma remote computer (e.g., a server) to a requesting computer (e.g., aclient) by way of one or more data signals embodied in and/or modulatedby a carrier wave or other propagation medium via a communication link(e.g., a modem and/or network connection). Accordingly, as used herein,a machine-readable medium may, but is not required to, comprise such acarrier wave.

The drawings and the forgoing description gave examples of the presentinvention. Although depicted as a number of disparate functional items,those skilled in the art will appreciate that one or more of suchelements may well be combined into single functional elements.Alternatively, certain elements may be split into multiple functionalelements. Elements from one embodiment may be added to anotherembodiment. For example, orders of processes described herein may bechanged and are not limited to the manner described herein. Moreover,the functions of any flow diagram need not be implemented in the ordershown; nor do all of the functions necessarily need to be performed.Also, those functionalities that are not dependent on other acts may beperformed in parallel with the other acts. The scope of the presentinvention, however, is by no means limited by these specific examples.Numerous variations, whether explicitly given in the specification ornot, such as differences in structure, dimension, and use of material,are possible. The scope of the invention is at least as broad as givenby the following claims.

What is claimed is:
 1. A method implemented by a base station,comprising: identifying by the base station available basic resourceblocks; determining by the base station possible tree structures for thebasic resource blocks; selecting by the base station one or more treestructure from the possible tree structures; storing by the base stationthe one or more selected tree structure in a codebook; and allocating bythe base station one or more basic resource block to a subscriberstation by indicating a code-book index and parent node, wherein theindicated code-book index is selected based at least in part on aquality of service (QoS) request.
 2. The method of claim 1, wherein atleast one basic resource block comprises a sub-channel that uses asub-channelization scheme selected from a group consisting ofdistributed and contiguous sub-carriers.
 3. The method of claim 1,wherein possible tree structures comprise (2^(L−1))! tree structures,where L is a number of levels in a tree structure.
 4. The method ofclaim 1, wherein selecting one or more tree structure from the possibletree structures comprises selecting 2^(K) tree structures, where 2^(K)is less than (2^(L−1))! and L is a number of levels in a tree structure.5. The method of claim 1, wherein selecting one or more tree structurefrom the possible tree structures comprises randomly selecting one ormore tree structure.
 6. The method of claim 1, wherein selecting one ormore tree structure from the possible tree structures comprisesselecting one or more tree based in part on subscriber station mobility.7. The method of claim 1, further comprising assigning a codebook indexto each of the selected one or more tree structure.
 8. The method ofclaim 1, wherein indicating a parent node comprises allocating childnodes under the parent node to the subscriber station.
 9. The method ofclaim 1, wherein storing the one or more selected tree structure in acodebook comprises providing each selected tree structure as a row ofthe codebook, wherein the codebook index refers to a row of thecodebook.
 10. The method of claim 1, further comprising communicating atleast one code book to one or more subscriber station, wherein at leastone code book includes blocks from at least one selected tree structureand wherein each codebook has an associated codebook index and includesat least one parent node.
 11. A base station configured to: identifyavailable basic resource blocks; determine possible tree structures forthe basic resource blocks; select one or more tree structure from thepossible tree structures; store the one or more selected tree structurein a codebook; and allocate one or more basic resource block to asubscriber station by indicating a code-book index and parent node,wherein the indicated code-book index is selected based at least in parton a quality of service (QoS) request.
 12. The base station of claim 11,wherein at least one basic resource block comprises a sub-channel thatuses a sub-channelization scheme selected from a group consisting ofdistributed and contiguous sub-carriers.
 13. The base station of claim11, wherein possible tree structures comprise (2^(L−1))! treestructures, where L is a number of levels in a tree structure.
 14. Thebase station of claim 11, wherein the base station is further configuredto select 2^(K) tree structures, where 2^(K) is less than (2^(L−1))! andL is a number of levels in a tree structure.
 15. The base station ofclaim 11, wherein the base station is further configured to randomlyselect one or more tree structure.
 16. The base station of claim 11,wherein the base station is further configured to select one or moretree based in part on subscriber station mobility.
 17. The base stationof claim 11, wherein the base station is further configured to assign acodebook index to each of the selected one or more tree structure. 18.The base station of claim 11, wherein the base station is furtherconfigured to allocate child nodes under the parent node to thesubscriber station.
 19. The base station of claim 11, wherein the basestation is further configured to provide each selected tree structure asa row of the codebook, wherein the codebook index refers to a row of thecodebook.
 20. The base station of claim 11, wherein the base station isfurther configured to communicate at least one code book to one or moresubscriber station, wherein at least one code book includes blocks fromat least one selected tree structure and wherein each codebook has anassociated codebook index and includes at least one parent node.